Test automation provides numerous benefits to software testing, and one of the key advantages is the reduction of repetitive manual work. This benefit is explicitly covered in the ISTQB Foundation Level Syllabus (v4.0).

Test automation allows testers to automate repetitive tasks such as regression testing, freeing up their time to focus on more complex and exploratory testing. This leads to improved efficiency and helps in avoiding human errors associated with repetitive tasks.

Option A: "More subjective assessment" contradicts the benefit of automation as it focuses on objectivity.

Option C: "Availability of the test automation tool vendor" is not a direct benefit of test automation, although vendor support can be valuable.

Option D: "Negligible effort to maintain the test assets" is misleading as maintaining automated tests often requires effort and attention to changes in the system under test.

Therefore, the correct answer is B​ (ISTQB not-for-profit association)​​ (ISTQB)​.